1.

). A train travelling at a uniform speed for 360 km would have taken48 minutes less to travel the same distance if its speed were 5 km/hrmore. Find the original speed of the train.

Answer»

Let original speed of train = x km/h

we know, time = distance/speed

first case time taken by train = 360/x hour

second case

time taken by train its speed increase 5 km/h = 360/( x + 5)

time taken by train in first - time taken by train in 2nd case = 48 min = 48/60 hour 360/x - 360/(x +5) = 48/60 = 4/5 360{ 1/x - 1/(x +5) } = 4/5 360 ×5/4 { 5/(x² +5x )} =1450 x 5 = x² + 5x x² +5x -2250 = 0x = { -5±√(25+9000) }/2 =(-5 ±√(9025) )/2 =(-5 ± 95)/2 = -50 , 45 but x ≠ -50 because speed doesn't negative so, x = 45 km/h hence, original speed of train = 45 km/h


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